Georgia State University ScholarWorks @ Georgia State University Computer Science Theses Department of Computer Science 5-4-2007 An Analysis of the MOS under Conditions of Delay, Jitter and Packet Loss and an Analysis of the Impact of Introducing Piggybacking and Reed Solomon FEC for VOIP Alexander F. Ribadeneira Follow this and additional works at: https://scholarworks.gsu.edu/cs_theses Part of the Computer Sciences Commons Recommended Citation Ribadeneira, Alexander F., "An Analysis of the MOS under Conditions of Delay, Jitter and Packet Loss and an Analysis of the Impact of Introducing Piggybacking and Reed Solomon FEC for VOIP." Thesis, Georgia State University, 2007. https://scholarworks.gsu.edu/cs_theses/44 This Thesis is brought to you for free and open access by the Department of Computer Science at ScholarWorks @ Georgia State University. It has been accepted for inclusion in Computer Science Theses by an authorized administrator of ScholarWorks @ Georgia State University. For more information, please contact [email protected]. AN ANALYSIS OF THE MOS UNDER CONDITIONS OF DELAY, JIITTER AND PACKET LOSS AND AN ANALYSIS OF THE IMPACT OF INTRODUCING PIGGYBACKING AND REED SOLOMON FEC FOR VOIP by ALEXANDER F. RIBADENEIRA Under the direction of Anu G. Bourgeois ABSTRACT Voice over IP (VoIP) is a real time application that allows transmitting voice through the Internet network. Recently there has been amazing progress in this field, mainly due to the development of voice codecs that react appropriately under conditions of packet loss, and the improvement of intelligent jitter buffers that perform better under conditions of variable inter packet delay. In addition, there are other factors that indirectly benefited VoIP. Today, computer networks are faster due to the advances in hardware and breakthrough algorithms. As a result, the quality of VoIP calls has improved considerably. However, the quality of VoIP calls under extreme conditions of packet loss still remains a major problem that needs to be addressed for the next generation of VoIP services. This thesis concentrates in making an analysis of the effects that network impairments, such as: delay, jitter, and packet loss have in the quality of VoIP calls and approaches to solve this problem. Finally, we analyze the impact of introducing forward error correction (FEC) Piggybacking and Reed Solomon codes for VoIP. To measure the mean opinion score of VoIP calls we develop an application based on the E-Model, and utilize perceptual evaluation of speech quality (PESQ). INDEX WORDS: VoIP, FEC, SIP, MOS, E-Model, PESQ, RTP, RTCP. AN ANALYSIS OF THE MOS UNDER CONDITIONS OF DELAY, JIITTER AND PACKET LOSS AND AN ANALYSIS OF THE IMPACT OF INTRODUCING PIGGYBACKING AND REED SOLOMON FEC FOR VOIP by ALEXANDER F. RIBADENEIRA A thesis Submitted in the Partial Fulfillment of the Requirements for the Degree of Master of Science in the College of Arts and Sciences Georgia State University 2007 Copyright by Alexander F Ribadeneira 2007 AN ANALYSIS OF THE MOS UNDER CONDITIONS OF DELAY, JIITTER AND PACKET LOSS AND AN ANALYSIS OF THE IMPACT OF INTRODUCING PIGGYBACKING AND REED SOLOMON FEC FOR VOIP by ALEXANDER F. RIBADENEIRA Major Professor: Anu G. Bourgeois Committee: Raheem A. Beyah Yingshu Li Electronic Version Approved: Office of Graduate Studies College of Arts and Sciences Georgia State University May 2007 iv DEDICATION To all the people who believe in social justice and peace. v ACKNOWLEDGEMENTS I would like to thank Dr. Anu Bourgeois for her guidance and support during this research. I also would like to thank to the members of the committee, Dr. Raheem A. Beyah and Dr. Yingshu Li for their helpful comments and suggestions. vi TABLE OF CONTENTS ACKNOWLEDGEMENTS................................................................................................ v LIST OF TABLES...........................................................................................................viii LIST OF FIGURES ........................................................................................................... ix LIST OF ABBREVATIONS .............................................................................................. x CHAPTER 1 – INTRODUCTION ..................................................................................... 1 CHAPTER 2 – BACKGROUND ....................................................................................... 4 2.1 Codecs....................................................................................................................... 4 2.2 Voice activity detection and silence suppression ..................................................... 6 2.3 Real time protocol..................................................................................................... 8 2.4 Real time control protocol ...................................................................................... 14 2.5 Jitter and jitter buffers............................................................................................. 15 2.6 Mean opinion score................................................................................................. 19 2.7 Signaling ................................................................................................................. 23 2.8 Session Initiation protocol ...................................................................................... 24 2.9 Constructing VoIP packets and throughput of one call with G.711 codec............. 27 2.10 A ratio of payload vs. packet length for codecs operating at 20 msec intervals... 29 2.11 Payload size per packet for G.711 and G.729 at different packet intervals.......... 32 2.12 Bandwidth consumption of G.711 and G.729 at different packet intervals. ........ 33 2.13 VoIP over wireless networks ................................................................................ 36 2.14 Security considerations for VoIP.......................................................................... 39 2.15 Recommendations for improving the quality of VoIP calls ................................. 42 vii CHAPTER 3 – PROBLEM DEFINITION....................................................................... 44 3.1 Factors that affect the quality of a VoIP call. ......................................................... 44 3.2 MOS under conditions of packet loss..................................................................... 46 CHAPTER 4 – ANALYSIS OF INTRODUCING FEC FOR VOIP ............................... 49 4.1 How to recover lost information in the event of packet loss. ................................. 49 4.2 Forward error correction......................................................................................... 50 4.3 Forward error correction with a piggybacking scheme .......................................... 51 4.4 Forward Error correction with Reed Solomon codes ............................................. 57 CHAPTER 5 – EXPERIMENTS AND RESULTS.......................................................... 67 5.1 Degradation due to loss of consecutive audio. ....................................................... 67 5.2 Call degradation on Cisco ATA 188 in the event of distinct forms of delay ......... 68 5.3 Call degradation on Grand Stream ATA in the event of distinct forms of delay ... 71 5.4 Call quality degradation with a fixed jitter buffer. ................................................. 74 5.5 Call quality degradation with an adaptive jitter buffer........................................... 77 5.6 MOS under the event of periodic and random lost (non-intrusive technique). ...... 80 CHAPTER 6 – CONCLUSION........................................................................................ 82 BIBLIOGRAPHY............................................................................................................. 87 APPENDIX....................................................................................................................... 91 APPENDIX A. RTP stream generator.......................................................................... 91 APPENDIX B. Mean opinion score calculator .......................................................... 101 viii LIST OF TABLES Table 2.1. [2]. Properties of Audio Encoding..................................................................... 5 Table 2.2. VoIP common codecs ........................................................................................ 6 Table 2.3. [2]. Payload types for audio encoding ............................................................. 11 Table 2.4 [23]. Mean Opinion Score ................................................................................ 20 Table 2.5. A ratio of payload vs. packet length ................................................................ 31 Table 2.6. Payload size per packet for G.711 and G.729 at different packet intervals..... 32 Table 2.7. Bandwidth consumption of the G.711 at different transmission cycles .......... 34 Table 2.8. Bandwidth consumption of the G.729 at different transmission cycles .......... 34 Table 4.1. Bandwidth consumption of FEC piggybacking scheme at 10 msec intervals. 53 Table 4.2. Bandwidth consumption of FEC piggybacking scheme at 20 msec intervals. 53 Table 4.3. Additional delay of FEC piggybacking scheme .............................................. 54 Table 4.4. Bandwidth consumption of FEC Reed Solomon code, T=10msec ................. 62 Table 4.5. Bandwidth consumption of FEC Reed Solomon code, T=20msec ................